According to experts, the rapidly spreading Omikron variant will probably not lead to the hoped-for herd immunity against the coronavirus. The problem, among other things, is the rapid mutation of the virus.
Since the early days of the pandemic, many have expressed hope that it would be possible to achieve herd immunity to Covid-19 if a high enough percentage of the population is vaccinated or infected with the virus. These hopes were dashed, however, when the coronavirus mutated in rapid succession last year into new variants that enabled it to re-infect people who had been vaccinated or previously infected.
Virus will find ways to overcome immune defenses
Although some health authorities, such as in Israel, have revisited the possibility of herd immunity since Omikron emerged late last year. They point to the fact that the Omikron variant is spreading so rapidly. And at the same time, the courses are milder, which may indicate that the pre-existing immune protection is working and weakening the disease-causing effect of the virus.
However, epidemiologists point out that the transmissibility of Omikron is favored by the fact that this variant is better able than its predecessors to infect people who are vaccinated or had a previous infection. Researchers see this as evidence that the virus is finding ways to overcome immune defenses and could continue to do so.
Whether Omikron remains mild is not certain
In an interview with Deutschlandfunk radio, the German Virologist Christian Drosten Said there were different ways omicron could evolve from a more mild variant into a more disease-causing one. The fear is that recombination of omicron and delta will happen, he said.
The reason for this is a change in the so-called spike protein. Therefore, the Omikron variant currently succeeds in bypassing the partially existing immune protection.
It is now conceivable that a virus will emerge in the future that, on the one hand, "carries the spike protein of the Omikron virus in order to continue to enjoy this immune advantage, but has the rest of the genome of the Delta virus," Drosten added. From both serotypes, "both worlds," the strongest characteristics could thus come together. "There is such a thing, it has already been described. The fear right now is that something like this could happen."
"Reaching a theoretical threshold at which transmission stops is probably unrealistic, given our experience with the pandemic," Olivier le Polain, an epidemiologist at the World Health Organization (WHO), told Reuters news agency.
But that doesn’t mean prior immunity is of no benefit, experts say: There is growing evidence that vaccines and prior infections boost the population’s immunity to Covid-19, which should at least lower the risk of severe disease progression.
Covid-19 cannot be kept in check like measles
"As long as population immunity continues with this variant and future variants, we’ll be lucky and the disease will be manageable," says David Heymann, professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine. Current covid-19 vaccines can primarily, prevent severe disease and death, but not infection.
The results of clinical trials for the approval of these vaccines at the end of 2020 showed that two doses of the vaccines produce an effectiveness of over 90 percent protection against the disease. How well the vaccines protect against infection initially remained an open question. The hope was that the vaccines would be so good at protecting against infection that they could contain corona similarly to what vaccines can do for measles. But that hope did not come true.
That’s for two reasons, says epidemiologist Marc Lipsitch, of Harvard T.H. Chan School of Public Health. "The first is that immunity, especially against infections, which is the most important type of immunity for containment, declines quite rapidly. At least with the vaccines that we currently have."Second, the virus can quickly mutate in such a way that it can evade the protective effect of a vaccination or a previous infection.
More immunity ≠ enough immunity
In an article in the U.S. journal The Atlantic, Virginia Pitzer, an epidemiologist at the Yale School of Public Health, estimates that 90 to 95 percent are likely to have been exposed to coronavirus through vaccination and/or infection after the Omicron surge in the U.S.
But this does not mean that these 90 to 95 percent are protected from infection or disease, analyzes the author of the article, Katherine J. Wu. That’s because more immunity doesn’t mean you’re sufficiently immune, he says. The problem, he said, is that currently no one can say how firmly individuals are protected. So whether person A (triple vaccinated, recently infected) has more protection than person B (twice infected, once vaccinated) or person C (once infected, unvaccinated).
"It’s a game changer when vaccinated people can still shed virus and infect other people," judges David Wohl, an infectious disease specialist at the Chapel Hill School of Medicine at the University of North Carolina. Wohl cautions against assuming omicron infection will increase protection, especially against next possible variant. "If you’ve had omicron, maybe that protects you from being re-infected with omicron, maybe."But not necessarily from infection with other variants.
This could be remedied by vaccines under development that provide immunity against future variants or even multiple types of coronaviruses, believes Pasi Penttinen, the European Center for Disease Prevention and Control’s lead influenza expert. But it takes time.
Endemic will come – but when?
The hope of a herd immunity as a ticket back to normal life is hard to shake. "These things have been in the media: ‘We will reach herd immunity when 60 percent of the population is vaccinated’. That didn’t happen. Then at 80 percent. That didn’t happen either," says Francois Balloux, Professor of computational systems biology at University College London.
"As horrible as it may sound, I think we have to be prepared for the vast majority, basically everyone, to come into contact with SARS-CoV-2." Experts believe coronavirus will eventually become endemic. Omikron has raised the question of when exactly this will happen, and, after Omikron, whether the endemic state might already have been reached. "We will get there," said WHO expert le Polain, "but right now we are not there yet".